Each year millions of cigarette smokers in the U.S. try to quit, only to fail within the initial days or weeks of the effort. Sustaining abstinence through the initial weeks of a cessation effort is associated with a precipitous decline in relapse risk. Indeed, there is substantial evidence in the literature on smoking and other drug abuse supporting strong associations between the duration of prior abstinence and relapse risk. What is missing and is the focus of this competing continuation are rigorous experimental studies examining how a period of early abstinence might protect against relapse risk. Such information has the potential to facilitate development of more focused and effective behavioral and pharmacological treatments. We are proposing 4 experiments involving three different experimental models of cigarette smoking to systematically analyze the relationship between initial abstinence and relapse risk. Primary among the models is a contingency-management arrangement that allows for experimental control over the amount of initial smoking abstinence achieved. Subjects will be daily cigarette smokers not currently trying to quit, but willing to abstain as part of a study. Subjects will earn payment by sustaining abstinence that is verified via 3 x/day CO monitoring. Nicotine withdrawal, craving, abstinence self-efficacy, mood, and related measures will be assessed daily. In Studies 1 and 2, subjects will be randomized to achieve 1-14 days of abstinence prior to undergoing a 3-hr relapse-risk challenge session assessing sensitivity to the relative reinforcing effects of smoking. In Study 1, the challenge session will involve a discrete-trial choice model in which subjects choose between cigarette smoking vs. monetary reinforcement. In Study 2, the challenge session will involve a progressive ratio (PR) model in which the number of operant responses necessary to earn smoking opportunities increases progressively throughout the session to estimate the maximal price that subjects will incur in order to smoke. In Study 3, we will use these same models to experimentally analyze the clinically important and related question of how brief "lapses" back to smoking alter the profile of withdrawal and related self-report measures as well as the relative reinforcing effects of smoking. Finally, in Study 4 we will use these same models to experimentally analyze how transdermal nicotine alters the relationships between initial abstinence, withdrawal and related measures, and the relative reinforcing effects of smoking. Overall, the proposed studies have the potential to efficiently and effectively contribute new, detailed information on how initial abstinence decreases relapse risk. Such information is essential to the development of more focused and effective smoking-cessation interventions.